95-Am-242MJAEA+ EVAL-JAN10 O.Iwamoto,T.Nakagawa,T.Ohsawa,+ DIST-MAY10 20100318 ----JENDL-4.0 MATERIAL 9547 -----INCIDENT NEUTRON DATA ------ENDF-6 FORMAT History 06-03 Fission cross section was evaluated with GMA code. 06-05 Resonance parameters were revised. 07-03 Fission spectra were evaluated (below 6 MeV). 07-05 Theoretical calculation was made with CCONE code. Resonance parameters were modified. 07-08 Theoretical calculation was made with CCONE code. 07-11 Theoretical calculation was made with CCONE code. 08-03 Interpolation of (5,18) was changed. Data were compiled as JENDL/AC-2008/1/. 09-03 (MF1,MT452) and (MF1,MT455) were revised. 09-08 (MF1,MT458) was evaluated. 10-01 Data of prompt gamma rays due to fission were given. 10-03 Covariance data were given. MF= 1 General information MT=452 Number of Neutrons per fission Sum of MT's=455 and 456. MT=455 Delayed neutron data Determined from nu-d of the following three nuclides and partial fission cross sections calculated with CCONE code/2/. Am-243 = 0.006659 *1) Am-242 = 0.0049 measured by Saleh et al./3/ Am-241 = 0.003154 *1) *1) an average of systematics by Tuttle/4/, Benedetti et al./5/ and Waldo et al./6/ Decay constants calculated by Brady and England./7/ were adopted. MT=456 Number of prompt neutrons per fission (same as JENDL-3.3) Maslov's evaluation/8/ was adopted. * MADLAND-NIX MODEL CALCULATIONS /9/ FITTED TO THE MEASURED DATA OF HOWE ET AL./10/ ABOVE EMISSIVE FISSION THRESHOLD SUPERPOSITION OF NEUTRON EMISSION IN (N,XNF) REACTIONS /11/ AND PROMPT FISSION NEUTRONS IS EMPLOYED. MT=458 Components of energy release due to fission Total energy and prompt energy were calculated from mass balance using JENDL-4 fission yields data and mass excess evaluation. Mass excess values were from Audi's 2009 evaluation/12/. Delayed energy values were calculated from the energy release for infinite irradiation using JENDL FP Decay Data File 2000 and JENDL-4 yields data. For delayed neutron energy, as the JENDL FP Decay Data File 2000/13/ does not include average neutron energy values, the average values were calculated using the formula shown in the report by T.R. England/14/. The fractions of prompt energy were calculated using the fractions of Sher's evaluation/15/ when they were provided. When the fractions were not given by Sher, averaged fractions were used. MF= 2 Resonance parameters MT=151 Resolved resonance parameters (below 43eV) Resonance parameters given in JENDL-3.3 were evaluated by Maslov et al./8/ For the current version, JENDL-3.3 parameters of 0.178eV resonance were modified so as to reproduce the thermal cross sections: fission = 6401+-134b /16,17,18,19, etc./ capture = 1147+-114b /19/ Unresolved resonance parameters (43eV - 20keV) Parameters were determined with ASREP code/20/ so as to reproduce the evaluated cross sections in the energy range from 43 eV to 20keV. They are used only for self-shielding calculations. Thermal cross sections and resonance integrals (at 300K) ------------------------------------------------------- 0.0253 eV reson. integ.(*) (barns) (barns) ------------------------------------------------------- total 7547.8 elastic 5.24 fission 6401.2 1550 capture 1141.4 236 ------------------------------------------------------- (*) In the energy range from 0.5 eV to 10 MeV. MF= 3 Neutron cross sections Cross sections above the resolved resonance region except for the total (MT=1), elastic scattering (MT=2) and fission cross sections (MT=18, 19, 20, 21, 38) were calculated with CCONE code/2/. MT=1 Total cross section From 43 eV to 10 keV, the total cross section was calculated as a sum of partial cross sections. Above 10 keV, the results of CCONE calculation were adopted. The calculation was made with CC OMP of Soukhovitskii et al./21/ The OMP was adjusted by Am-241(n,tot) cross section/22/. MT=2 Elastic scattering cross section From 43 eV to 10 keV, calculated with CCONE code. Above 10 keV, calculated as the total - non-elastic scattering cross sections. MT=51 (n,n') to 1st level Calculated with CCONE code. Below 1 eV, 1/v shape was assumed. MT=18 Fission cross section (Above 43eV) The following experimental data were analyzed with the GMA code /23/: Aleksandrov+/24/, Fomushkin+/25/, Dabbs+/16/, Browne+/17/, Shigin+/26/, Fursov+/27/, Kai+/18/ Above 14MeV, the cross section was determined by eye-guiding. The results of GMA were used to determine the parameters in the CCONE calculation. MT=19, 20, 21, 38 Multi-chance fission cross sections Calculated with CCONE code, and renormalized to the total fission cross section (MT=18). MF= 4 Angular distributions of secondary neutrons MT=2 Elastic scattering Calculated with CCONE code. MT=18 Fission Isotropic distributions in the laboratory system were assumed. MF= 5 Energy distributions of secondary neutrons MT=18 Fission neutron spectra Below 6 MeV, calculated by Ohsawa/28/ with modified Madland- Nix formula considering multi-mode fission processes (standard-1, standard-2, superlong). Above 7 MeV, calculated with CCONE code. MT=455 Delayed neutron spectra Summation calculation by Brady and England /7/ was adopted. MF= 6 Energy-angle distributions Calculated with CCONE code. Distributions from fission (MT=18) are not included. MF=12 Photon production multiplicities MT=18 Fission Calculated from the total energy released by the prompt gamma-rays due to fission given in MF=1/MT=458 and the average energy of gamma-rays. MF=14 Photon angular distributions MT=18 Fission Isotoropic distributions were assumed. MF=15 Continuous photon energy spectra MT=18 Fission Experimental data measured by Verbinski et al./29/ for Pu-239 thermal fission were adopted. MF=31 Covariances of average number of neutrons per fission MT=452 Number of neutrons per fission Combination of covariances for MT=455 and MT=456. MT=455 Error of 20% was assumed. MT=456 Experimental data of Howe et al./10/ were fitted with a straight line and covariance data were obtained. MF=32 Covariances of resonance parameters Format of LCOMP=0 was adopted. Covarinaces of JENDL-3.3 /30/ were adopted. MF=33 Covariances of neutron cross sections Covariances were given to all the cross sections by using KALMAN code/31/ and the covariances of model parameters used in the theoretical calculations. For the following cross sections, covariances were determined by different methods. MT=1, 2 Total and elastic scattering cross sections In the resonance region (below 1 keV), uncertainty of 10 % was added. MT=18 Fission cross section Above the resonance region cross section was evaluated with GMA code/23/. The following uncertainties were addeded to the GMA results. 43 eV to 1 keV 10 % 1 keV to 100 keV 5 % 0.1 MeV to 1 MeV 3 % MT=102 Capture cross section In the resonance region, the following uncertainties were added. 1 to 5 eV 5 % 5 to 10 eV 10 % 10 to 43 eV 15 % Above 43 keV, covariance matrix was obtained with CCONE and KALMAN codes/31/. MF=34 Covariances for Angular Distributions MT=2 Elastic scattering Covariances were given only to P1 components. MF=35 Covariances for Energy Distributions MT=18 Fission spectra Below 6 MeV, covarinaces of Pu239 fission spectra given in JENDL-3.3 were adopted after multiplying a factor of 9. Above 6 MeV, estimated with CCONE and KALMAN codes. ***************************************************************** Calculation with CCONE code ***************************************************************** Models and parameters used in the CCONE/2/ calculation 1) Coupled channel optical model Levels in the rotational band were included. Optical model potential and coupled levels are shown in Table 1. 2) Two-component exciton model/32/ * Global parametrization of Koning-Duijvestijn/33/ was used. * Gamma emission channel/34/ was added to simulate direct and semi-direct capture reaction. 3) Hauser-Feshbach statistical model * Moldauer width fluctuation correction/35/ was included. * Neutron, gamma and fission decay channel were included. * Transmission coefficients of neutrons were taken from coupled channel calculation in Table 1. * The level scheme of the target is shown in Table 2. * Level density formula of constant temperature and Fermi-gas model were used with shell energy correction and collective enhancement factor. Parameters are shown in Table 3. * Fission channel: Double humped fission barriers were assumed. Fission barrier penetrabilities were calculated with Hill-Wheler formula/36/. Fission barrier parameters were shown in Table 4. Transition state model was used and continuum levels are assumed above the saddles. The level density parameters for inner and outer saddles are shown in Tables 5 and 6, respectively. * Gamma-ray strength function of Kopecky et al/37/,/38/ was used. The prameters are shown in Table 7. ------------------------------------------------------------------ Tables ------------------------------------------------------------------ Table 1. Coupled channel calculation -------------------------------------------------- * rigid rotor model was applied * coupled levels = 2,6,10 (see Table 2) * optical potential parameters /21/ Volume: V_0 = 48 MeV lambda_HF = 0.004 1/MeV C_viso = 15.9 MeV A_v = 12.04 MeV B_v = 81.36 MeV E_a = 385 MeV r_v = 1.255 fm a_v = 0.58 fm Surface: W_0 = 17.2 MeV B_s = 11.19 MeV C_s = 0.01361 1/MeV C_wiso = 23.5 MeV r_s = 1.15 fm a_s = 0.601 fm Spin-orbit: V_so = 5.75 MeV lambda_so = 0.005 1/MeV W_so = -3.1 MeV B_so = 160 MeV r_so = 1.1214 fm a_so = 0.59 fm Coulomb: C_coul = 1.3 r_c = 1.2452 fm a_c = 0.545 fm Deformation: beta_2 = 0.243 beta_4 = 0.08 beta_6 = 0.0015 * Calculated strength function S0= 1.26e-4 S1= 2.08e-4 R'= 9.60 fm (En=1 keV) -------------------------------------------------- Table 2. Level Scheme of Am-242 ------------------- No. Ex(MeV) J PI ------------------- 0 0.00000 1 - 1 0.04409 0 - 2 0.04860 5 - * 3 0.05270 3 - 4 0.07582 2 - 5 0.09900 2 + 6 0.11400 6 - * 7 0.14800 5 - 8 0.14969 4 - 9 0.17100 4 - 10 0.19000 7 - * 11 0.19770 3 - 12 0.23053 1 + 13 0.24436 3 - 14 0.26300 6 - 15 0.26990 3 + 16 0.27433 1 - 17 0.28350 7 + 18 0.28901 4 - 19 0.29284 2 - 20 0.29641 2 - 21 0.30700 5 + 22 0.32784 3 - 23 0.33071 3 - 24 0.34158 0 + 25 0.34200 5 - 26 0.35569 2 + 27 0.36470 2 + 28 0.37040 4 + 29 0.37247 4 - ------------------- *) Coupled levels in CC calculation Table 3. Level density parameters -------------------------------------------------------- Nuclide a* Pair Eshell T E0 Ematch 1/MeV MeV MeV MeV MeV MeV -------------------------------------------------------- Am-243 17.8584 0.7698 2.0985 0.4029 -0.9548 3.1071 Am-242 18.6337 0.0000 1.6845 0.2795 -0.6541 0.9592 Am-241 18.1961 0.7730 1.7328 0.3819 -0.7226 2.8365 Am-240 18.5012 0.0000 1.3474 0.2883 -0.6831 1.0000 Am-239 18.4349 0.7762 1.5592 0.3648 -0.5528 2.6354 -------------------------------------------------------- Table 4. Fission barrier parameters ---------------------------------------- Nuclide V_A hw_A V_B hw_B MeV MeV MeV MeV ---------------------------------------- Am-243 6.200 0.800 5.150 0.520 Am-242 6.410 0.600 5.800 0.550 Am-241 6.100 0.800 5.500 0.520 Am-240 6.100 0.650 6.000 0.450 Am-239 6.000 0.800 5.400 0.520 ---------------------------------------- Table 5. Level density above inner saddle -------------------------------------------------------- Nuclide a* Pair Eshell T E0 Ematch 1/MeV MeV MeV MeV MeV MeV -------------------------------------------------------- Am-243 21.5049 0.8981 2.6000 0.2555 -0.6419 2.0981 Am-242 20.8697 0.0000 2.6000 0.3254 -2.4113 2.0000 Am-241 21.3526 0.9018 2.6000 0.3213 -1.4929 2.9018 Am-240 21.2764 0.0000 2.6000 0.3219 -2.3947 2.0000 Am-239 21.2001 0.9056 2.6000 0.3225 -1.4891 2.9056 -------------------------------------------------------- Table 6. Level density above outer saddle -------------------------------------------------------- Nuclide a* Pair Eshell T E0 Ematch 1/MeV MeV MeV MeV MeV MeV -------------------------------------------------------- Am-243 21.5049 0.8981 0.6000 0.3532 -0.8019 2.8981 Am-242 21.4288 0.0000 0.5600 0.3688 -1.8681 2.2000 Am-241 21.3526 0.9018 0.5200 0.3556 -0.7969 2.9018 Am-240 21.2764 0.0000 0.4800 0.3567 -1.6981 2.0000 Am-239 21.2001 0.9056 0.4400 0.3579 -0.7919 2.9056 -------------------------------------------------------- Table 7. Gamma-ray strength function for Am-243 -------------------------------------------------------- * E1: ER = 11.52 (MeV) EG = 2.77 (MeV) SIG = 244.72 (mb) ER = 14.31 (MeV) EG = 4.19 (MeV) SIG = 489.44 (mb) * M1: ER = 6.57 (MeV) EG = 4.00 (MeV) SIG = 1.28 (mb) * E2: ER = 10.10 (MeV) EG = 3.19 (MeV) SIG = 6.92 (mb) -------------------------------------------------------- References 1) O.Iwamoto et al.: J. Nucl. Sci. Technol., 46, 510 (2009). 2) O.Iwamoto: J. Nucl. Sci. 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